/Engine/Source/Runtime/CoreUObject/Public/UObject/Object.h
Called from within SavePackage on the passed in base/root object. The return value of this function will be passed to PostSaveRoot. This is used to allow objects used as a base to perform required actions before saving and cleanup afterwards.
virtual void PreSaveRoot ( [FObjectPreSaveRootContext](API\Runtime\CoreUObject\UObject\FObjectPreSaveRootContext) ObjectSaveContext )